U.S. Pat. No. 4,975,354 issued Dec. 4, 1990, entitled "Photographic Element Comprising An Ethyleneoxy-Substituted Amino Compound And Process Adapted To Provide High Contrast Development", by Harold I. Machonkin and Donald L. Kerr, describes silver halide photographic elements having incorporated therein a hydrazine compound which functions as a nucleator and an amino compound which functions as an incorporated booster. Such elements provide a highly desirable combination of high photographic speed, very high contrast and excellent dot quality, which renders them very useful in the field of graphic arts. Moreover, since they incorporate the booster in the photographic element, rather than using a developing solution containing a booster, they have the further advantage that they are processable in conventional, low cost, rapid-access developers.
While the high-contrast photographic elements of U.S. Pat. No. 4,975,354 represent a major advance in the art, there is a continuing need to improve the properties of these photographic elements, for example, to provide increased photographic speed and even higher contrast. Moreover, enhanced developability of these high-contrast elements, which would enable the use of very short development times, would also be highly beneficial in the field of graphic arts.
It is a well known expedient to increase photographic speed by the use of chemical sensitizing agents, and a very wide variety of different compounds are known to be useful as chemical sensitizers (see, for example, Research Disclosure, Issue No. 308, Item 308119, Paragraph III, December, 1989). However, the use of chemical sensitizing agents can adversely affect other properties of silver halide emulsions which contain a hydrazine compound that functions as a nucleator and an amino compound that functions as an incorporated booster, for example, it can adversely affect contrast or result in an increase in fog.
It is toward the objective of providing an improved high-contrast photographic element--containing both a hydrazine compound that functions as a nucleator and an amino compound that functions as an incorporated booster--that has enhanced developability and that exhibits increased speed and increased toe contrast, without a concurrent increase in fog, that the present invention is directed.